Greece has accused German Finance Minister Wolfgang Schäuble of insulting his Greek counterpart, the latest deterioration in a relationship badly strained by Berlin’s tough line on Athens’ debt woes.

The hawkish Schäuble, who has become a lightning rod for Greek frustrations, was quoted in Greek media as telling reporters after EU discussions on Greece in Brussels that Yanis Varoufakis was “foolishly naive” in his communications.

“There was an official complaint from our ambassador in Berlin to the German Foreign Ministry on Tuesday night,” Greek Foreign Ministry spokesman Constantinos Koutras said on Thursday.

“It was a complaint after what he (Schäuble) said about Mr. Varoufakis. As a minister of a country that is our friend and our ally, he cannot personally insult a colleague.”

Koutras did not specify what the alleged insult was. Foreign media covering Schäuble in Brussels did not report the “foolishly naive” comment, leading to suggestions in some local newspapers that he might have been mistranslated.

Greece’s new leftist government was elected on a vow to relax the conditions of a 240 billion euro ($250 billion) bailout, which it says have suffocated its economy, causing mass unemployment and poverty.

However, Varoufakis has so far made little headway against the EU, most of which has backed Germany’s insistence on rigorous financial austerity.

With ties already at a low ebb, Greece this week renewed its campaign to seek compensation for the Nazis’ brutal occupation in World War II, an issue that Berlin says was settled decades ago.

“A debt must be a debt and a debt everywhere… especially those which are weighed down by historical significance,” Varoufakis told France 24.

“Unless of course, we all decide that debts can be forgiven and can be restructured,” he added.

Berlin argues that the issue of reparations to Greece has already been settled in 1960 as part of an agreement with several European governments.

Varoufakis told Greek television on Wednesday that he had “great respect” for Schäuble, but signalled that there were strains:

“Mr. Schäuble has told me I have lost the trust of the German government. I have told him that I never had it. I have the trust of the Greek people.”

Indeed, according Der Spiegel, Varoufakis’ version of Greece has always been a hard sell for Schäuble. To the German finance minister, it remains as threatening and profligate as the center-right edition that preceded it.

“It won’t be good for Europe if we are too generous with the Greeks,” he told the German periodical in February. “We are on the right path towards leaving the euro crisis behind us…. We can’t allow that to be ruined by a country that doesn’t follow any rules.”